In general, color photographic silver halide photosensitive material, after exposure, is processed through steps of color development, desilvering, washing, and stabilization. Color developers are used for color development, bleaching, bleach-fixing, and fixing solutions used for desilvering, city water or ion exchanged water used for washing, and stabilizers used for stabilization. Typically color photosensitive material is processed by dipping in the respective solutions which are usually adjusted to 30.degree. to 40.degree. C. The color development and desilvering steps are essential among these steps.
In the color development step, the exposed silver halide is reduced with a color developing agent to generate silver whereupon the oxidized color developing agent reacts with a color former or coupler to provide a dye image. In the subsequent desilvering step, the silver generated in the color development step is oxidized by the bleaching agent serving as an oxidizing agent and dissolved away by the fixing agent serving as a complex ion forming agent for silver ion. As a result, only the dye image is formed.
The desilvering step includes a procedure of conducting bleaching and fixing in a common bath, a procedure of conducting bleaching and fixing in separate baths, or a procedure of conducting bleaching and bleach-fixing in separate baths. Each of the baths can have multiple tanks.
In addition to the above-mentioned basic steps, various supplemental steps are taken for the purposes of maintaining photographic and physical properties of dye images and improving storage quality. Such supplemental steps are done in hardening, stop, stabilizing, wash and other baths.
The foregoing steps are generally carried out in automatic processors. In general, automatic processors perform continuous processing in either a "replenishment" or "batch" mode. The replenishment mode is to make up replenishers in amounts proportional to the quantity of color photosensitive material processed in order to keep the performance of processing solutions constant. The batch mode is to replace all or part of used processing solutions with fresh solutions whenever the quantity of color photosensitive material processed reaches a predetermined level. Among the two modes, the replenishment mode is often employed for ease of operation.
At the very start of a continuous process or at the restart of a continuous process after replacement of exhausted solutions by fresh solutions, an automatic processor adapted for the replenishment mode is sometimes operated with its processing tanks filled with replenishers as such. However, most replenishers as such are insufficient to provide desirable photographic performance. Therefore, solutions having a somewhat different composition from the replenishers are separately prepared and used as processing solutions (known as mother solutions) at the start.
The processing solutions used at the start include two types, that is, a special kit of reagents and a replenisher having added thereto a modifying agent known as "starter" and optionally water. Particularly in small photographic service laboratories called "mini labo", a system using the "starter" is often employed.
Typically, a bleaching solution used in the desilvering step is also based on the starter system, that is, prepared by combining a starter with a bleaching replenisher. The bleaching starter contains a compound (alkaline agent) which becomes basic or alkaline when dissolved in water. In general, the bleaching solution is designed such as to provide a desired pH level for photographic performance from the start as an alkaline color development solution a color photosensitive material carries in from the preceding bath intermixes with a low pH bleaching replenisher. The alkaline agents used in the prior art are ammonia, potassium hydroxide, and sodium hydroxide.
These prior art alkaline agents, however, have problems associated with handling and photographic performance. For example, ammonia water gives off a foul smell and readily vaporizes so that the effective concentration of ammonia lowers. Potassium hydroxide and sodium hydroxide are not only dangerous to the skin upon contact because they are strong alkalis, but tend to absorb carbon dioxide in air so that their effective concentration lowers as in the case of ammonia. They often cause iron hydroxide to precipitate when combined with ferric aminopolycarboxylic acid complexes widely used as the bleaching agent.
In addition to these problems or as a result of these problems, the foregoing alkaline agents, especially potassium hydroxide and sodium hydroxide cause a lowering of bleaching rate, detracting from desilvering ability. Such a loss of desilvering ability becomes outstanding particularly when quick processing is to be done, often disturbing quick processing.